1. Technical Field
The present invention relates in general to the detection of errors in seismic data and in particular to apparatus for detecting errors in frames of seismic data that can be presented as images.
2. Description of the Related Art
Due to the techniques used for collecting seismic data, an image produced to represent that data will typically be expected to exhibit an inherent symmetry about an axis. However seismic survey data is subject to various errors from many causes; the most frequent cause of errors are background noise and misplaced equipment. Analysis of the seismic data is typically a very long process with the data passing through many stages of computational processing. Hence it is desirable to identify errors in frames of data as early as possible to avoid wasting valuable time processing bad data. A reliable technique for detecting errors could save much re-work.
Typically a company involved in obtaining and analyzing seismic data will have to transport a great deal of hardware to the survey location, will carry out a large number of seismic tests, and then will return to the laboratory to analyze the data. Seismic tests usually involve positioning cables in lines on the surface of the land (or towing cables behind a ship on the surface of water), each cable having a number of sensors attached to it along its length. A shock wave is then generated, eg. by firing a shot, at a location on the surface symmetrically disposed with respect to the cables, and the shock waves are detected along these cables of sensors. Given this type of arrangement, it is apparent that viewing the collections of signals as an image and checking for symmetry is a good way of detecting errors.
However, up until now, this has been done by geophysicists checking by eye. Obviously this is very time consuming, labor intensive, and prone to errors, and so it would be highly desirable to reduce the time that a geophysicist must spend inspecting the data. The seismic industry has applied theories of geophysics in an attempt to solve the problem of error detection, but has been unable to solve the problem purely within the domain of geophysics.